Tupis Todd M, Altman Gregory T, Altman Daniel T, Cook Harold A, Miller Mark Carl
Allegheny General Hospital, Pittsburgh, PA, USA.
Clin Biomech (Bristol). 2012 May;27(4):354-9. doi: 10.1016/j.clinbiomech.2011.11.002. Epub 2011 Dec 2.
Antegrade femoral nailing has become the standard treatment for diaphyseal femoral shaft fractures. Concerns linger that improper location of the nail entry point may lead to iatrogenic fracture and further complications. This study used finite element analysis to compare the strain magnitude and distribution resulting from each of two entry points in the proximal femur during antegrade nailing.
A finite element model was created from a CT scan of a 37 year old male femur and of a standard antegrade nail. Using implicit time-stepping, the nail was inserted through piriformis and trochanteric entry points and strain was computed at 9 anatomic locations.
The strain levels were higher overall when inserting a nail through the trochanteric starting point. The highest strain occurred immediately medial and lateral to the trochanteric entry point. The posterior greater trochanter also showed very high strain levels during nail insertion. All strain values for nail insertion through the piriformis entry point were less than 2000 μm/m.
The trochanteric entry will have a much greater potential of iatrogenic fracture of the proximal femur during insertion of a nail. Strains with this entry point exceed the yield level of bone and the repeated loading with the progression of the nail could cause fissures or fractures. Caution should be taken during insertion of an antegrade nail when utilizing a lateral trochanteric starting point secondary to an increased risk of trochanteric fracture and lateral cortex fracture.
顺行股骨髓内钉固定术已成为股骨干骨折的标准治疗方法。人们一直担心钉入点位置不当可能导致医源性骨折及进一步的并发症。本研究采用有限元分析比较顺行髓内钉固定时股骨近端两个不同钉入点所产生的应变大小及分布情况。
利用一名37岁男性股骨的CT扫描数据及标准顺行髓内钉建立有限元模型。采用隐式时间步长法，将髓内钉分别经梨状肌和大转子入点插入，并计算9个解剖位置的应变。
经大转子起始点插入髓内钉时，总体应变水平更高。最高应变出现在大转子入点的内侧和外侧紧邻处。在插入髓内钉过程中，大转子后部也显示出非常高的应变水平。经梨状肌入点插入髓内钉时的所有应变值均小于2000μm/m。
在插入髓内钉时，经大转子入点导致股骨近端医源性骨折的可能性要大得多。该入点处的应变超过了骨的屈服水平，随着髓内钉的推进反复加载可能会导致骨裂或骨折。当采用大转子外侧起始点进行顺行髓内钉固定时，由于大转子骨折和外侧皮质骨折的风险增加，应谨慎操作。
